Field of Invention
The present invention relates to a spot welding apparatus, and more particularly, to a spot welding apparatus which allows welding to be performed at a plurality of welding points, and simultaneously allows welding to be performed while varying a welding pitch in accordance with a distance between the respective welding points, thereby quickly performing welding work in a limited space for a minimum period of time.
Description of Related Art
In general, in a process of manufacturing a vehicle, an integral vehicle body is completed by bonding various structural components such as vehicle body panels, which are formed by a press, by a welding method, or the like. In a painting process, painting work, and rust prevention work are performed on a surface of each of the components of the completed vehicle body, and thereafter components of a power train system and components of suspension, steering, and brake systems are assembled. Next, a design process of assembling doors, a trunk lid, a hood, or the like is performed.
In addition, in a vehicle body assembly process for a vehicle, in order to bond components of the vehicle body such as a roof, pillars, side panels, opening part flanges of vehicle body doors, a spot resistance welding method is widely used as a method of bonding two sheets of vehicle body panels.
The spot resistance welding method refers to a method of welding the vehicle body panels using electrical resistance while applying pressure to surfaces of the vehicle body panels. Referring to FIG. 1, the spot resistance welding method is typically performed by a C-type spot welding gun 5 that is installed on a front end of an arm 3 of a robot 1 for spot welding.
Referring to FIG. 2, the spot welding gun 5 has a lower electrode 13 and an upper electrode 15, which are coupled to a C-type gun body 11, and the upper electrode 13 is connected to a drive cylinder 17 that is installed at one side of an upper portion of the gun body 11 and provides pressure.
In a state in which the gun body 11 is installed on the front end of the arm 3 of the robot 1 through an installation frame 19, the spot welding gun 5 is positioned at a welding position in accordance with behavior of the robot 1 and performs the spot welding for an object to be welded by an operation of the drive cylinder 17.
Meanwhile, in the spot welding process for assembling the vehicle body, since continuous welding needs to be performed along typically tens to hundreds of positions of welding points, a long period of time is needed, and the work processes are very complicated. Therefore, various methods are being sought to shorten a welding time and improve productivity, efficiency, and welding quality.
However, in a general welding system, because one welding apparatus 5 can be attached to the robot arm 3 of one robot 1, and the welding can be performed for only one spot for every moment when the arm 3 of the robot moves, a very long period of time is needed to perform the welding for a predetermined number of welding points, and thereby there is a problem in that productivity and efficiency deteriorate.
To avoid the aforementioned problem, a plurality of robots can be installed and can simultaneously perform the welding while being moved along the positions of the welding points, but if a plurality of robots, which is expensive, has a complicated configuration, and requires a complicated control process, is used, there are problems in that costs for equipment and maintenance are increased, excessive energy is used, and a spatial occupancy rate of the robot is increased in a mass-production line.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.